By Robert McCaffrey, conference convenor

The conference started with a presentation from Michele Graffigna from HeidelbergCement, who gave some details on the Italcementi acquisition and the use of alternative fuels (AF) in the combined group. Due to the acquisition, HeidelbergCement created a new Mediterranean region with 19 plants. Spanish landfill costs are still low, but around 50% of waste is handled by MRF plants all the same. Countries like Morocco show great potential, with a large cement sector and relatively low AF usage age. However, the first shipment of refuse-derived fuel (RDF) from Italy was stopped at the port and import of waste-derived fuels was banned. This has led to a greater effort to create RDF from local waste. On the other hand, the fuel crisis in Egypt in 2013 drove the whole sector towards the use of alternative fuels. The Kattameya waste treatment facility was the first to be based at a cement plant in Egypt and other projects have driven AF use in HeidelbergCement plants in the country.

The second presentation was given by Joe Harder of OneStone Consulting, who spoke on global trends in AF. He pointed out that a huge range of AF usage rates exists through the industry, from plants burning no AF to plants that can and do use 100% AF substitution. Joe stated that in Europe the thermal substitution rate is around 39%, whereas in North America it is only 5%. In the Netherlands the rate is around 85%, down to 23% in Spain and only 7% in Greece. China’s rate is currently 2%, but is said to be rising fast. The use of AF in Germany has plateaued at around 60%, partly due to economics, partly due to supply and partly due to technical issues. Due to its purchase of selected assets from Lafarge and Holcim, the Ireland-based CRH is now the world’s leading cement producer in terms of AF use, with a company-wide thermal substitution rate (TSR) of 39%, followed by Cemex on 26% and HeidelbergCement on 21%. Generally producers in developing countries use a higher proportion of biofuels - which Joe Harder suggested should be secondary byproducts, rather than being specially produced since these crops will compete for land and resources with food crops. The coal price is not tied to the oil price, stated Joe, and since the summer of 2016 the price of thermal coal has started to increase again after five years of steady declines, leading to an increase in interest in the use of AF. Joe pointed out that Geocycle, established in the 1970s by Holcim, now operates in more than 40 countries and has over 2000 employees. This is a model that other cement companies could usefully copy and try to improve upon. Dr Harder suggested that a number of cement companies have set challenging targets for AF use, some of which are challenging enough that they are unlikely to be met. Coal and petcoke prices, availability of AF and cement capacity growth, and the availability of pre-treatment facilities will be major criteria for the future development of the use of AF.

Andy Hill next gave a presentation with a very short title, ‘EU AF,’ but which Andy described as a huge topic. An increase in immigration into Germany has led to an increase in production of waste and an oversupply of SRF, while Russian bans on cement imports and Indian demonetisation have also led to pressure on SRF prices. Other uncertainties are Brexit, the rise of Donald Trump, and China’s sustainability push. China’s ‘Green Fence’ policy is increasing quality control on imported waste and may eventually lead to the end of waste imports. There is a global oversupply of waste at the moment, so a Chinese ban would strongly impact on prices and profitability elsewhere in the industry. On the other hand, Europe currently ‘loses’ around 600Mt of waste each year to landfill that could be used as fuels and for other uses. Around 30% of municipal waste still ends up in landfill, although there is a 2030 target of only 10%, EU-wide. An extension of ‘Extended producer responsibility’ legislation should lead to more inherently recyclable products, and a reduction in supply for RDF. At the same time, competition from the waste-to-energy (WtE) sector is likely to increase. CO2 prices are likely to increase, possibly to Euro40/t, by 2030, although the European cement industry may cease to be competitive at a rate of around Euro20/t. Plastics production will continue to grow worldwide, while paper recycling is at a high level already. The bulk of recycled paper is shipped to China, but again, higher quality barriers may decrease the amount admitted to China in the future. RDF has a CV value up to 15MJ/kg, while SRF has a calorific value (CV) of above 15MJ/kg and is generally a highly processed ‘engineered’ fuel. Andy said that the market for SRF worldwide is around 60Mt. SRF is increasingly being pelletised, meaning that it can then be more easily co-processed and incinerated with coal. Freight rates are starting to rise again from historic lows, with price increases also being seen in container rates. Andy suggested that oil prices are now unlikely to rise above $75 per barrel due to the impact of American drillers.

Vagner Maringolo of Cembureau next spoke about opportunities for increased waste take-up for the European cement industry. Vagner points out that the EU is moving towards a ban on landfilling for municipal waste, which will give a strong boost to the supply of alternative fuels. A Cembureau/Ecofys study on the market potential of AF brought up a number of interesting conclusions. Around 10Mt of waste was co-processed in cement kilns in the EU28 in 2015, representing around 2% of total combustible waste each year, but representing 10% of all of the energy recovery from waste in the EU.

Jaime Ruiz de Haro, president of Cemex Spain and president of Oficemen, the Spanish Cement Producers’ Association, next spoke about the development of AF in Spain. Average cement consumption in Spain in the last 50 years was 25Mt/yr. However, consumption spiked to more than 50Mt in 2007, and has plummeted to just over 10Mt in 2016, a demand level last seen in the 1960s, precipitating a huge crisis in the cement and construction industry. Spain is the largest exporter of cement and clinker in Europe. In Spain, 29 of the 33 Spanish cement plants are authorised to use AF, and 77 types of waste have been authorised for use in Spain. The tonnage of AF used in Spain has plateaued at 700 - 800,000t/yr for the last five years, at a TSR of around 24%. RDF is the mostly widely used AF, at over 250,000t/year, followed by tyres (100,000t), biomass and animal meal. De Haro pointed out that high disposal fees strongly drive the use of AF in the cement industry, and he suggested that stronger implementation and enforcement of regulations and fees will be the main driver of increased AF use in the country. In Spain a realistic target has been set to use 30% TSR by 2020, 45% by 2030, and 70% by 2050.

Mrs Dalia Sakr of the International Finance Corporation spoke about the use of AF in Egypt, starting with the energy crisis of 2013 when gas supplies were diverted from the cement industry to the power industry. This caused a fall in production of 50% and this caused the industry to move strongly towards not only increased use of coal but also increased use of AF. Mrs Sakr introduced a major study of potential sources of AF in Egypt, including RDF, agricultural waste, dried sewage sludge and tyre-derived fuel (TDF). Agricultural waste is the largest waste stream of more than 30 - 35Mt each year, but production is geographically widely spread and the material has relatively low CV. Each year Egypt generates more than 21Mt of municipal waste, forecast to reach 35Mt by 2025. At the moment only around 0.5Mt is used each year, but the best case scenario would be to use around 5Mt/year. Around 1Mt of sewage sludge is produced each year, but a major challenge is to reduce its moisture content to economic levels. The amount of tyres produced each year is estimated at around 300,000t, but only 10% of this amount is used by the cement industry. On the AF demand side, the Egyptian cement industry has a TSR of only around 7% but the majority of cement plants in Egypt have active plans to start to use or to use more AF in the next five to ten years. One of the main problems is that a gigajoule of energy from AF is not appreciably less expensive than energy from coal or petcoke. The quality and security of the supply is also an issue, and Mrs Sakr stated that regulatory support will be required to improve the quality of waste-derived fuels. As in other countries, the enforcement and increase in tipping fees will strongly drive the availability of AF in Egypt.

In the event’s next session, on alternative fuels production advances, Daniel Wresnik of Untha spoke about new trends in SRF production. Daniel suggested that a strong trend in the industry is towards single-step shredding. He introduced several completed projects including Geocycle projects in Vietnam, the US and Mexico. Requests from the industry led to the company to develop the XR mobil-e mobile shredder. Both the mobile and stationary shredders use slow-running single shaft shredding for rough, medium and fine shredding of waste.

Next, Eric Plantié of Precimeca introduced the tyre-shredding capabilities of his company, which include both stationary and mobile tyre shredders. The company has striven towards clean-cut and homogeneous size of chips as well as a consistent output through the lifetime of the knives and no exposed beading wires that could lead to the clogging of the dosing system. Tyre supply is not prone to seasonality of supply and offers 25 - 30MJ/kg (6-7000kcal/kg), allowing nearly 1:1 substitution by weight with coal or petcoke. TDF has a bulk density of around 0.5t/m3, is almost incompressible and can be stored outside with no ill-effects. TDF has a chlorine content of <0.1%, and sulphur content of less than 1.5%, making it a relatively easy-to-use alternative fuel. Eric mentioned a case study of a LafargeHolcim cement plant with a TSR of 60% using 70,000t of AF, of which 3000t is whole tyres and 15,000t was imported tyre chips of inferior quality. The plant specified that, instead of using imported chips, a new tyre shredder would have to produce 10t/hour of clean cut product, at a particle size of lower than 50mm. The plant settled on a fully-automatic stationary tyre shredder with two high-torque low-speed shearing rotors, capable of accepting tyres up to a maximum diameter of 1200mm. The rotors will automatically reverse rotation direction to prevent any potential jam. The system includes a tyre chip classifier to ensure that all output is of below 50mm chip size.

Neville Roberts of fuel-producer N+P next spoke on the subject of SubCoal SRF pellets. N+P has a reference plant at Delfzijl in the Netherlands for SubCoal production, and pellets have been shown to be hydrophobic, while being capable of being co-ground with coal. SubCoal has a CV of 23.8MJ/kg, and can be transported in containers, with no de-baling required at the end user, unlike some other types of AF. Loesche vertical roller mills and Atritor grinding systems have both been used to grind SubCoal pellets. N+P is busy setting up SubCoal production facilities closer to a number of cement industry users around Europe, including a new Euro14m 120,000t/yr production plant at Teesport, near Middlesborough in the UK. SubCoal pellets from the plant will have moisture content of less than 8%, with CV of more than 20GJ/t, with the majority of the output of the plant destined for export, not just to the cement industry.

The first presentation in the next session, on AF handling storage and dosing, was given by Juan Jose Riesgo of FLSmidth Pfister on the AF system at the Cementos Portland Valderrivas Monjos plant, which had been visited by delegates the previous day. Juan mentioned some pieces of equipment that can be supplied by FLS that can aid in the use of AF, including Feedex waste storage and handling, the Koch pipe conveyor, the Pfister Rotor weighfeeder, the Hotdisc AF combustor and the Jetflex burner. The company’s equipment is capable of coping with both dense and light AF, down to 0.05t/m3. In fact at Monjos, the company, with partners, built a flexible waste reception, handling, mixing and dosing facility capable of handling a wide variety of AF, including petcoke, RDF, MBM, dried sewage sludge (DSS) and wood. Juan mentioned some useful experience from the project; RDF needs to have a moisture content of less than 30% to avoid handling problems; chlorides need to be lower than 2% to avoid pyroprocessing blockage issues; the fat content of MBM needs to be lower than 16% to avoid it sticking to walls; wood had issues with self-combustion after fermentation in hot weather and turned out to be non-economic. Truck unloading should be done carefully to avoid spillages, while wear issues can be found in pneumatic pipelines and in the weighfeeder when using certain types of AF. Silos for the storage of AF should be shorter and wider than normal, just the opposite of silos for storage of traditional fuels. It has been found that the average maintenance bill for the full AF system, including spares, service and manpower, is in the region of Euro100,000 per year.

Global CemFuels Awards Dinner

The Global CemFuels Awards Dinner took place at the UNESCO-listed Recinte Modernista de Sant Pau, close to the Sagrada Familia in Barcelona. The ‘outstanding AF project’ award went to HeidelbergCement’s Lengfurt cement plant in Germany, which burns 100% AF, while HeidelbergCement itself won the award for ‘global AF-using company of the year.’ N+P of the Netherlands won the award for ‘global AF-supplying company of the year.’ The ‘most innovative technology for AF’ prize was awarded to Lindner-Recyclingtech’s Polaris single-shaft shredder; ‘project manager of the year’ was awarded to Marco Mater of AVE, Portugal, and the award for outstanding contribution for the promotion of AF was presented to the CEMA Foundation of Spain. The award was accepted by Jaime Ruiz de Haro, president of Cemex Spain and president of Oficemen, the Spanish Cement Producers’ Association. The Global CemFuels ‘personality of year’ award was presented to the widely-admired 90-year old industry stalwart Sebastian Rosin of Atritor Ltd. It was announced to acclaim that the location of the 12th Global CemFuels Conference will be Berlin.

Conference second day

On the second day of the conference, Michael Gramling of MHC Engineering Fördertechnik GmbH started by giving details of an innovative drag chain conveyor design for space-constricted cement plants. He pointed out that the wide variety of physical characteristics of AF in terms of density, moisture, stickiness and particle size distribution and shape means that they are much more difficult to handle than classic cement-making materials such as limestone, gypsum and clinker. Michael Gramling went through the advantages and disadvantages of inclined belt conveyors, inclined sandwich conveyors, inclined chain conveyors, bucket elevators and vertical chain conveyors, concluding that the vertical chain conveyor offers strong advantages for conveying AF in a space-constrained cement plant.

Basri Ogut of the ATS Group next gave some details of case studies of handling AF in the cement industry, including two case studies at Ultratech Aditya Cement in India and Cimat Beni Mellal in Morocco. Basri introduced an extraction and dosing machine named the Doseahorse, incorporating AF extraction and dosing in the same machine.

Luigi Di Matteo of the Di Matteo Group next pointed out that the coarser particle size of AF means that devolatilisation is slower, ignition is later, burnout needs more residence time and unburned particles may fall into the clinker bed. He went on to outline his company’s wide capabilities in manufacturing equipment to handle, dry, dose and feed AF.

The final paper in the session on handling, storage and dosing was given by Jose Diaz of Schenck Process Europe, specifically on dosing technology for AF. He mentioned the MultiFlex compact closed AF weighfeeder and the MultiDos belt weigh feeder, for a feed rate of 1 - 30t/hour. The weigh feeders can be used in conjunction with a novel swirl air chamber for calciner feeding.

A pair of papers on the influence of AF on clinker quality were up next, the first of which was given by Stéphane Poellaer of Alterline. He stated that to be able to start to use AF, the first prerequisite is for preexisting stable operation in the kiln and pyroprocessing system. Stéphane suggested that AF feeding should first be tried at the calciner burner, being the most ‘forgiving’ point of feeding, before moving to introduce AF at the main burner. Lumpy fuels that cannot be suspended in the gas stream in the calciner can be problematic. High alkaline contents of AF will lead to innumerable problems, including corrosion, refractory expansion, thermal shocks, ring formation and blockages. AF will also affect the flame temperature and shape, while clinker quality will be affected in a number of ways, including by the ash content of the AF. He suggested that each tonne of AF fed to the system will reduce the clinker output by two tonnes, unless systematic steps are taken to mitigate the deleterious effects of AF combustion. He concluded that “AF does not make life easier, but it makes life more interesting.”

Carmen Gheorghe of Geocycle (Romania) went on to describe a study of clinker and cement produced with and without use of AF, using a variety of analytical techniques. Certainly, the overall chemical composition is not influenced by AF use, while at the same time the mineralogical composition is also more or less unchanged, albeit with more C3S and lower free lime in the AF sample. Porosity is slightly increased in AF-produced clinker leading to a marginally more grindable clinker. Carmen suggested that 7 and 28 day strengths of mortar cubes were also very similar.

In the conference’s final session, on combustion optimisation, Xavier d’Hubert of Nexa Industries gave an overview of burners for rotary kilns. Xavier suggested a threefold categorisation of burners into fixed multi-channel burners, burners that mix or separate the axial and radial primary air inside the burner, and a third category of burners with axial primary air jet ejection angles that are adjustable. He suggested that there has been a general trend from low NOx burners towards burners that are capable of firing a variety of solid alternative fuels.

Matthias Schumacher of aixergee Process Optimisation next spoke on a novel approach to answering the question ‘what particle size is RDF?’ Lumpy fuels may be subject to ‘rain out’ segregation from the burner flame in the kiln, causing unstable kilns and leading to reducing conditions in the clinker bed and yellowish or brown clinker. Rain-out can also happen in the calciner, despite high gas velocities, causing coatings on the shelf and balls in the kiln. Milled coal is of practically spherical shape, with homogeneous and constant particle density, whereas waste derived fuels have a vast number of variable physical parameters, of which particle size is just one. Particle shape and material density are also factors which strongly affect pneumatic transport properties and performance in the flame. Particle shapes of RDF will include flat, cuboid, cubic, and ‘spherical’ (but of very low density, like a ball of wool), with these shapes increasing in sphericity. Matthias suggested that a ‘particle sifting velocity’ distribution should be used, which finds the air velocity required to suspend the different particles, to describe the behaviour of particles in the pyroprocessing system.

The penultimate presentation was given by Joel Maia of FCT GmbH, on a case study at Urmia cement in Iran. The company found itself priced out of the fuel oil market and was obliged to use natural gas. However, the emissivity of a natural gas flame is lower than a fuel oil flame and is at a lower temperature, which brings process challenges, including a higher exhaust gas volume for the same thermal power, higher CO, a lower calcination degree at the calciner exit and higher temperature at the top of the preheater tower. The suggestion was that the plant might purchase four new calciner burners, but it was decided that a CFD study should be first undertaken. It was found that burning natural gas in the calciner with burners in the existing situation would lead to nearly 2% of the gas not being burned within the calciner, with the remainder existing as CO, and this was deemed to be unacceptable. It was decided to add two gas combustion lances into the top of the tertiary air duct, and this was shown to improve the velocity profile and the temperature distribution, leading to better refractory lining protection, better heat transfer to the meal and better ignition of the natural gas. It was also shown that the previously proposed calciner burners would not have solved the problem.

The closing keynote speech was given by Ed Verhamme, who proposed ‘Twelve and a half’ principles of a money-making strategy for the use of AF. His principles were as follows: know the basics of waste management and adhere to the waste hierarchy principles; know the waste and resource markets and value chains; make a weighted decision as to where to enter the value chain; recognise the differences between the waste and cement businesses; lobby for the co-processing of waste resources; get flexible environmental permits; use flexible pre-processing equipment; know the cement process and effects of AF on the system; set realistic technical and economic cement and AF goals; get the backing of senior management; develop long term contracts; and develop a shareholder engagement plan. Finally, he concluded in his twelve and a halfth principle, that you should celebrate your success with everyone involved.

Conference Farewell and prizes

At the conference farewell reception, a number of prizes were awarded. Grupo SPR won for ‘best exhibition stand.’ Carmen Gheorghe of Geocycle was in third place in the best presentation awards, for her paper on the affects of AF on cement and clinker quality, while Stéphane Poellaer of Alterline was in second place with his paper on the impact of alternative fuels on kiln process. However, in first place, and winner of the ‘best presentation award,’ was Xavier d’Hubert of Nexa Industries, with his paper on burner choices.

The conference was strongly rated by delegates, especially for its technical content and usefulness for making contacts. Attendees agreed to meet at the next Global CemFuels, in Berlin.